1. Field of the Invention
This invention relates to a transistor structure, and more particularly to a vertical transistor and an array of a vertical transistor.
2. Description of Related Art
In order to accelerate operating speed of integrated circuits and to meet customers' demands for miniaturizing electronic devices, physical dimensions of transistors in a semiconductor apparatus are continuously reduced. However, with the reduction in physical dimensions of transistors, the length of channel regions in the transistors is also reduced. Thus, a severe short channel effect would occur in the transistors, and its ON current is likely to decrease. A conventional solution to said issue is to enhance the dopant concentration in the channel region. Nevertheless, this method causes an increase in a leakage current and therefore affects the reliability of devices.
Hence, to resolve said issue, a conventional horizontal transistor structure is recently replaced by a vertical transistor structure in the industry. For example, the vertical transistor structure is formed in the deep trench of the substrate. Hence, the operating speed and integration of integrated circuits are enhanced and problems such as short channel effect are avoided. Currently, improvements in structural design and channel control of the existing vertical transistors are studied aggressively in this field.